With the rapid development of communication networks, the synchronization requirements of the networks are higher and higher. Being able to extract a real-time time from each node of the network means a lot to the application and maintenance of the network. Especially in the significant promotion of the current 3GPP (Third Generation Partnership Project) technology, the mobile data service is increasing rapidly, which further proposes higher requirements on the data service support ability of the bearer network. The service provision of various 3GPP networks depends on high precision time synchronization in the network to different degrees.
Currently, the time synchronization method used in the existing network is mainly to provide a GPS (Global Positioning System) receiving device in each node of the network and perform precise time service depending on the GPS system. However, when using this method, not only the cost and the construction difficulty are high, but also the security cannot be ensured since the entire network depends entirely on the GPS system of America.
Based on the above reasons, the prior art usually employs the manner of combining high precision time protocol IEEE1588 protocol with GPS to realize the time synchronization of the network. This method requires adding of some network resources in the original network system to run the time synchronization protocol. In addition, it is further required to provide an external time source in a node, and then this node is used as a GM (GrandMaster) node of the network, the GM node provides a time service for the entire network by setting the GPS receiver, and various nodes in the network send a PIP (Precision time Protocol) message to each other by running the IEEE1588 protocol, in order to realize synchronization of the slave nodes to the master node and finally realize the time synchronization of the entire network. This method can provide network time synchronization for remote time synchronization devices. At the same time, when the GPS system is not secure enough, it can be changed over to other external time sources in time, which ensures the security of the network to a great extent, and therefore, it can be promoted rapidly in the development of time synchronization.
Now, during application, the operator further proposes that the GM node introduces the 1 PPS (1 Pulse Per Second) signal and TOD (Time Of Date) time information acquired from the GPS system via the GPS port and FE (Fast Ethernet) port. However, since only one of the two ports can be in an operating state, once the current operating port has failed, there is still no effective solution proposed in the prior art about how to change over to another port to introduce time information, thus being unable to realize the effective changeover of the externally connected time port.